With increase in interest in solar cells, much attention has been placed on improving the process of manufacturing the solar cells. One of sub-processes in manufacturing the solar cell may be a doping process to alter electrical and/or optical property of the solar cell. In a conventional doping process that requires patterned doping a resist or silicon dioxide (“passivating”) layer, portions of the passivating layer may be removed, and portions of the solar cell may be exposed. On the exposed portions, a glass containing n-type dopants (e.g. phosphorous) may be placed. Additional portions of the passivating layer may then be removed from the surface, and another glass containing p-type dopants (e.g. boron) may be placed.
Heat may then be applied to the solar cell. With the application of heat, both n-type and p-type dopants from the glasses may diffuse into the solar cell, forming n-type and p-type doped regions. The glasses originally containing the dopant materials may then be removed.
The conventional doping process, however, is not without disadvantages. For example, the conventional solar cell manufacturing process requires the doped glasses to intimately contact the solar cell. If contaminants such as voids or air bubble are present at the glass/solar cell interface, the contaminants may hinder the doping process and/or the doping process may not form uniform doped regions.
In addition, the passivating layer and the doped glasses may be made from a material having a low melting and/or glass transition temperature. As such, excessive heat may release contaminants and introduce the contaminants to the solar cell. Moreover, excessive heat may degrade the structural integrity of the passivating layer. The contaminants and the degradation structural integrity may lead to unstable and/or non-repeatable doping condition and/or formation of non-uniform doped regions.
To prevent such disadvantages, materials having higher melting temperature, such as crystalline quartz, may be used. However, cost of the materials having higher melting temperature is very high, and use of such materials for manufacturing solar cells may be impractical. Alternatively, less heat may be applied to the solar cell. Application of less heat, however, may not provide uniform doped regions.
Another disadvantage of the conventional solar cell manufacturing process is its use of the diffusion process to form the doped regions. As known in the art, success of forming uniform doped regions may depend on parameters such as dopant concentration gradient in both of the doped glasses and the solar cell and application of uniform temperature, parameters that are difficult to control. As such, forming uniform doped regions via the conventional diffusion process may be difficult.
Yet another disadvantage of the conventional doping process may be found in the efficiency of the process. In particular, for a solar cell design requiring patterned doping, the conventional manufacturing process may require additional steps for forming the passivating layer, performing lithography and etching processes to remove portions of the passivating layer, placing the doped glasses, and performing an etching process to remove the glasses.
Such disadvantages may decrease the quality of the solar cell and/or increase the cost of manufacturing the solar cell, placing additional financial burden on the manufactures and, ultimately, the consumers. As such, improved systems and methods for manufacturing the solar cells are needed.